Technical Abstract:
The rare plant taxon, "Fragaria multicipita" Fernald, is characterized by dwarfing, a cushion-like growth habit with multiple crowns, lack of runners, and development of floral aberrations suggestive of a subarctic or ice front relict. First described in 1908 from Canada, the species was thought to be extinct until its rediscovery in 1992. Recently, a pathogen was graft transmitted by others from F. multicipita to normal F. chiloensis; disease symptoms developed in the grafted F. chiloensis. Our data indicate that F. multicipita and the grafted F. chiloensis were infected by phytoplasma. We classified the phytoplasma in 16S rRNA gene group 16SrVI (potato witches broom and related phytoplasmas), but the F. multicipita phytoplasma belonged to a new subgroup, which we designated 16SrVI-B. Our findings indicate that "F. multicipita" is a unique growth form induced in Fragaria by phytoplasmal infection. While this study was in progress, we investigated a disease problem in winter production fields of strawberry in Florida. To obtain fruit production in Florida, most transplants are raised in northern areas of North America, especially Canada, where cool nights induce flower bud initiation. We found that some diseased strawberry plants in Florida were infected by a phytoplasma that was not distinguished from the phytoplasma which we believe to be responsible for the unusual growth form of "F. multicipita". Our data are consistent with a possible link between phytoplasmal infection of "F. multicipita" in natural ecosystems in Canada and diseased strawberry plants in Florida, and they point to a natural reservoir of inoculum for infection of cultivated strawberry.